The present invention relates in general to spindles for wheel mounting in automotive vehicles, and, more specifically, to the attachment of cast iron or steel spindles to cast aluminum wheel carriers.
The use of lightweight materials in automotive vehicles is desired wherever possible in order to help increase fuel economy. Thus, the use of aluminum instead of iron or steel in vehicle suspension components is of increasing interest to vehicle manufacturers. However, the material properties of aluminum can be very different from those of steel or iron, meaning that aluminum cannot be directly substituted in every component in a straightforward way.
A vehicle suspension includes a spindle to which a wheel hub is mounted. The spindle is mounted to a wheel carrier such as a knuckle, axle, or other component. Due to strength and heat transfer requirements, the spindle is typically made of ferrous material, such as steel or iron. Prior art spindles have previously been made as an integral forging/casting with their carrier or have been mounted to their carriers by threading, welding, or press-fitting into a bore, for example.
One hurdle in the possible use of aluminum castings for wheel carriers has been the lack of an easy method to attach the spindle. Prior art mounting methods have been unsuccessful due to the distinct properties of steel/iron versus aluminum, such as aluminum""s greater susceptibility to concentrated stress.
The present invention provides a spindle to aluminum wheel carrier mounting with increased contact area for reducing stress in the aluminum. As used herein, xe2x80x9caluminumxe2x80x9d includes any alloy principally comprised of aluminum.
In one aspect of the invention, a wheel assembly for a vehicle comprises a spindle, a wheel carrier, and a fastener. The spindle is comprised of ferrous material and includes a shank portion, a boss portion, and a fastening portion. The boss portion has a monotonically changing diameter along its longitudinal axis. The wheel carrier is adapted to be supported by a suspension system of the vehicle and has a wheel-facing side. The wheel carrier is comprised of aluminum and has a spindle-receiving aperture therethrough. The aperture has a variable diameter along its length to form a boss-receiving socket. The boss-receiving socket has a monotonically changing diameter substantially matching the boss portion. A fastener is joined to the fastening portion and draws the boss portion against the boss-receiving socket. Consequently, stresses in the aluminum wheel carrier are distributed over the boss-receiving socket.